Conventional animals used for production of antibodies are, for example, the mouse, the rat, the sheep and the goat. These mammals, however, have their proteins which are highly similar to the human proteins and therefore, it is often difficult to produce an antibody that suppresses function of a specific human protein by using these animals. In other words, even if these animals are immunized against a human molecule (for example, a human protein) that relates to a certain disease, it was often difficult to produce a desired antibody (particularly, an antibody for treatment) within these animals.
On the other hand, the production of anti-human antibodies for treatment or diagnosis by using the chicken, which is far apart from the human, has been recently attempted (for example, Japanese Laid-Open Patent Publication No. 2001-238676). However, this method has the problem that it is difficult to produce a large amount of homogeneous antibodies, because the chicken has very little blood. Moreover, a conventional method for producing a monoclonal antibody has the problem that many cell cultures, media for the cell cultures and complicated work are needed in order to produce a sufficient amount of antibodies.